Recently, techniques have been spread which reduce the capacity of a storage device for storing audio signals or reduce the amount of communications of transmission and reception by carrying out compression encoding such as AAC (Advanced Audio Codec) or MP3 (MPEG Audio Layer 3) rather than by using conventional audio CDs. The compression-encoded audio signal, however, has a tendency to lack impact of a low-range component and to reduce depth of sounds.
Thus, Patent Document 1, for example, proposes an effector for improving a low-range component of a compression-encoded audio signal. FIG. 6 is a block diagram showing a configuration of an effector 10 proposed by the Patent Document 1. The effector 10 uses, as its input, an audio signal obtained by decoding a musical signal with a high compression ratio such as AAC and MP3, and a gain assigning circuit 11 assigns different nonlinear gains to a positive waveform portion and a negative waveform portion of the input audio signal. Next, from a high-range component of the input audio signal to which the nonlinear gain is assigned by the gain assigning circuit 11, a high-range component creating circuit 12 creates an audio signal component with a range higher than the high-range component. Likewise, from a low-range component of the input audio signal to which the nonlinear gain is assigned by the gain assigning circuit 11, the low-range component creating circuit 13 creates an audio signal component with a range lower than the low-range component. Then, an addition combining circuit 14 adds and combines the input audio signal to which the gain is assigned with the high range audio signal component and the low-range audio signal component. Thus, it can improve the sound quality of the input audio signal. In particular, as for the low range, since the low-range component creating circuit 13 generates the low-range component with a frequency lower than the low range of the input audio signal, it can achieve powerful low-range emphasis effect.